negotiate (default): The encapsulation will select ISL or dot1q, whichever both ends of the trunk support. If both end supports both types, ISL is favored.

What is the default native VLAN used by 802.1Q?

vlan 1

What is the point of “switchport trunk allowed vlan” ?

Defines which VLANs can be trunked over the link.

Default: all vlans allowed

How do you configure dynamic trunking protocol (DTP)?

(interface)switchport mode …

trunk
The port is configured as trunk statically. If the other side is trunk, dynamic desirable or dynamic auto, trunking will be negotiated successfully.

dynamic desirable (default)
The port actively attempts to convert the link into trunking mode. If the other side is trunk, dynamic desirable or dynamic auto, trunking will be negotiated successfully.

dynamic auto
The port can be converted into a trunk link, but only if the far-end switch actively requests it. If the other side is trunk or dynamic desirable, trunking will be negotiated successfully.

How often DTP frames are sent?

every 30 seconds

What happens to DTP when “switchport access” is configured?

DTP will still send frames. If you want to disable DTP entirely use:switchport nonegotiate

What happens when DTP communicates to a non-cisco device?

It cannot communicate to a non-cisco device since DTP is Cisco proprietary protocol.
You should always disable DTP

What happens when you prune a vlan from the “allowed vlan” list, but only one side?

Wireless VLANs

What operational modes do switches have?

Autonomous mode: The AP operates independently and directly connects VLANs to WLANs on a one-to-one basis.

Lightweight mode: The AP must join with a wireless LAN controller. The AP connects each of its own WLANs with a VLAN connected to the controller. All of the VLAN-WLAN traffic is encapsulated and carried over a special tunnel between the AP and the controller.